Ocean Optics OOIBase32 (from Dr. David Chesney) - of Peter Gottlieb

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g. g. Scope Modeh. h. Absorbance Modei. i. Transmission Modej. j. Irradiance Modek. k. Configure Spectrum and Viewl. l. Autoscalem. m. Set Scalen. n. Unscaleo. o. Toggle Cursorp. p. Cursor Peak Leftq. q. Cursor Big Leftr. r. Cursor Lefts. s. Cursor Rightt. t. Cursor Big Rightu. u. Configure Cursor2. 2. We will ignore the second row of buttons for now.3. 3. Directly above the spectrum display area is a row of response boxes. Weare only concerned with the first three for now. From the left:Integ. Time (Integration Time)AverageBoxcar4. 4. With the spectrometer in Scope Mode (blue S showing), adjust theIntegration Time to cause the highest peak in the spectrum to read about3500 counts on the y-axis. See this spectrum.5. 5. Adjust the value in the Average box to change the number of discretespectral scans to accumulate before showing a spectrum. Note that thehigher the value, the smoother the resulting spectrum. Also, the longer ittakes to refresh the spectrum. The signal-to-noise ratio of the spectrumimproves by the square root of the number of spectra averaged. A value of32 is a suitable compromise.6. 6. Adjust the value in the Boxcar box. Note that the higher the value, thesmoother the resulting spectrum. However, if the value entered becomes toolarge, a significant loss in spectral resolution results. A value of 10-12 isreasonable for UV-Vis spectra.7. 7. Depress the Store Reference button.8. 8. Block the light beam. The spectrum should be just a straight line alongthe bottom of the display. Depress the Store Dark button.9. 9. Un-block the light beam. You should have a spectrum similar to whatyou had previously in the display window.
What you did: The fiber optic cable transmits different wavelengths of light tovarying degrees. (Note that the “spectrum” in the display is not of uniformintensity from left to right.) You need to subtract this “cable spectrum” from youranalytical spectra.The dark spectrum corrects for any signal output which does not originate at thecuvette holder.HOWEVER, the “cable spectrum” will change if you vary the position of the cableor any of the modules of the spectrometer system. Hence, it is very importantthat you do not move any part of the spectrometer system once you havestored a reference (cable) spectrum. If you do move the components, you needto take and store another reference and dark spectrum.Of course, the “cable spectrum” also changes if you change the acquisitionparameters (Integ. Time, Average and Boxcar). If you change any of theseparameters, you must take and store a new reference and dark spectrumbefore proceeding.Absorbance Measurements1. 1. In Scope Mode with an empty cuvette in place in the cuvette holder,adjust the acquisition paramters (Integ. Time, Average and Boxcar) toproduce a suitable signal. Take and store a reference spectrum.NOTE: In many cases, you need a reference spectrum of yoursolvent. In that case, take the reference spectrum at this pointwith clean solvent in your cuvette.2. 2. Remove the cuvette and block the light beam. Take and store a darkspectrum. Do not change any data acquisition parameters (Integ. Time,Average or Boxcar) from this point on without taking new reference anddark spectra.3. 3. Replace the empty cuvette.4. 4. Click on Absorbance Mode in the button bar. Your spectrum shouldhave zero absorbance across the selected wavelength range.5. 5. Adjust scale parameters with the Set Scale button.Typically, the Absorbance axis ranges from 0 – 1 A.U.
Page 4 and 5: (Absorbance Unit), and the waveleng
Page 6 and 7: Experiment with moving the cursor.

Ocean Optics OOIBase32 (from Dr. David Chesney) - of Peter Gottlieb

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